This invention is relating to an apparatus for the even tightening of a series of elastic and non-elastic bands of the type as fitted to the frames of pieces of furniture such as armchairs, settees or the like.
This apparatus is particularly designed for tightening bands which require a substantial force to be tightened and which are subject to undergo a minimum elongation.
The apparatus according to this invention is characterized in that it is simple in construction and, thus, easy and practical to use, as well as of lower cost as compared with other, known apparatus for performing the same function.
When manufacturing pieces of furniture such as armchairs, settees, chairs or the like, it is often usual to fit the frames of these pieces of furniture with series of parallel belts made of elastic material, to which a stuffing material is subsequently mounted as necessary.
These belts have to be tightened in a uniform manner and, to this end, machines are provided for putting a plurality of parallel belts or bands in tension and for fitting them to support frames of pieces of furniture, which machines are arranged to supply the belts and to tighten them with a substantially uniform force.
One of these machines known is disclosed in Italian Patent N. 979.355 granted Sep. 30, 1974, and comprises a set of rolls causing the parallel bands to move to a working table, and means for inverting the direction of rotation of said rolls so as to tighten the bands after an operator has attached the ends thereof to a frame of piece of furniture to permit the bands to be fixed to an opposite side of the frame, whereupon the bands are cut.
These machines also include sensing means to sense tension of the bands, which are able to stop the tension rolls automatically.
Said means is a roll mounted to pneumatic supports which press the roll against the bands. When a force of reaction produced by the bands, upon the bands reaching a required tension, acts so as to cause this roll to move backwardly, a microswitch will operate to stop operation of the machine.
However, some problems arise with this known apparatus when the bands to be fitted to a frame are elastic bands requiring a high tension and having a minumum rate of elongation.
In this apparatus, in fact, the belts run between a pair of opposed rolls which cause the bands to advance and which subsequently apply a pull thereon to put the bands under tension, and, in case of high strength bands, it would be necessary for these bands to be tightened between the rolls with a substantial amount of pressure which is often such as to be likely to damage the bands. In a similar manner, it would be also necessary for the tension roll to be subjected to a great pressure which may give rise to many troubles as a result.